1. Field of the Invention
The present invention relates to injectable sustained release drug delivery devices, and processes useful for making such devices.
2. Brief Description of the Related Art
U.S. Pat. No. 6,375,972, by Hong Guo et al., incorporated by reference herein in its entirety, describes certain drug delivery devices using various combinations of drug cores and polymer coatings to control a delivery rate of drugs implanted into living tissue. While having significant advantages, the reduction in the size of such devices as a part of a normal product development cycle can make manufacture of the devices more difficult. As described in the '972 patent, the drug reservoir can be formed within the tube which supports it by a number of different methods, including injecting the drug matrix into the preformed tube. With smaller tubes and more viscous drug matrix materials, this technique becomes increasingly difficult.
One approach to this difficulty is disclosed in an article by Kajihara et al. appearing in the Journal of Controlled Release, 73, pp. 279-291 (2001), which describes the preparation of sustained-release formulations for protein drugs using silicones as carriers. The disclosure of this article is incorporated herein in its entirety.
Another approach to reducing the size of sustained-release drug delivery systems is disclosed in U.S. pat. app. Ser. No. 10/428,214, filed May 2, 2003. While that disclosure is not limited to devices of any particular size, the co-extrusion techniques disclosed therein are amenable to the manufacture of small devices.
Despite the inherent difficulties in manufacturing small, sustained-release drug delivery devices, such devices have started to approach sizes where injection of the device becomes a possibility. However, there remains a need for improved injectable sustained-release drug delivery systems and techniques for making the same.